Summary The Lufthansa German Airlines Boeing 747-430 aircraft, flight number DLH471, was parked at pad5 at Toronto/ Lester B. Pearson International Airport (LBPIA) central de-icing facility while de-icing procedures were being carried out on the aircraft. After completing the de-icing procedure on the right wing, the operator of vehicle13, one of four vehicles applying de-icing/anti-icing fluid to DLH471, observed that the wing root was still contaminated. The vehicle operator asked permission from the zone de-icing controller to pass in front of the Boeing 747's engines to apply a second coating of de-icing fluid to the area. He was not able to communicate with the zone de-icing controller on the congested company UHF radio and maintained a position 15 feet inboard of the aircraft's right wing tip. Assuming that the de-icing procedures were complete and that the equipment was clear of the path of the aircraft, Iceman issued the aircraft a taxi authorization out of the central de-icing facility. When the de-icing vehicle operator saw that DLH471 was beginning to move forward, he attempted to move the vehicle to a safe position away from the path of the oncoming aircraft. The right leading edge of the aircraft's wing struck the boom just below the extended cab of vehicle13, tipping the vehicle over on its right side. The de-icing vehicle operator sustained non-life-threatening injuries to the head, face, and lower left leg. The de-icing vehicle's cab was destroyed, and the right leading edge wing skin of the Boeing747 was damaged. The accident occurred at 2146 Eastern standard time. Ce rapport est galement disponible en franais. Other Factual Information The de-icing procedures at Toronto / Lester B. Pearson International Airport, Ontario, are controlled using a radio communication system. When an aircraft requires de-icing before departure, the flight crew advises apron control at the same time as they request an authorization to push back from the terminal gate. The aircraft is pushed back, the engines are started, and the flight crew calls apron control again when the aircraft is ready to taxi. Apron control authorizes the aircraft to exit the apron at a specified exit point and advises the flight crew to switch to Toronto ground control frequency before the aircraft enters the taxiway. Ground control then gives the flight crew taxi route instructions and a taxi clearance to the central de-icing facility (CDF). The aircraft is routed via taxiway Tango, Victor, Mike, or Echo, the only taxiways to enter the CDF. (See Appendix A.) Before reaching the CDF, the aircraft is instructed to hold short of the de-icing pads and to contact Iceman to request routing instructions to one of the six de-icing pads. The authorization from Iceman includes instructions to follow the Follow Me truck to the specified de-icing pad. (See Appendix B.) The flight crew is told to advise Iceman when the aircraft is stopped in position with the brakes set and the aircraft configured for de-icing. Iceman confirms with the flight crew that the aircraft is ready for de-icing and advises them to monitor the lit sign board, which displays Stop and two red lights throughout the de-icing process. Iceman also tells the flight crew when the application of de-icing/anti-icing fluid begins. All radio communications with apron control, ground control, and Iceman use published common VHF radios. Zone de-icing controllers (ZDCs), however, have a UHF radio to communicate with the de-icing vehicles on a discrete frequency. ZDCs communicate with as many as four de-icing vehicles per pad, normally to a maximum of three pads. These UHF communications are recorded. Along with the usual radio traffic from the de-icing vehicle operators, there is also itinerant UHF radio traffic from roaming quality assurance personnel, de-icing supervisors, and other staff vehicles. The company has no instructions or procedures limiting the number of de-icing pads that one ZDC can oversee at once. Similarly, it has no instructions or procedures limiting the number of company UHF operators on one frequency. The de-icing vehicles (beta trucks) are operated by a single driver/operator. From the operator's cab, on a hydraulically actuated boom, the operator can manoeuvre the truck, extend or retract the boom, and manipulate the de-icing fluid spray cannon. When de-icing heavy aircraft, standard operating procedures call for four de-icing vehicles. The six de-icing pads lie east/west and have a safe zone clearly marked on the south and north side of each pad. When preparing to de-ice a heavy aircraft on pad 5, two beta trucks would wait in the safe zone south of pad 5 and two beta trucks would wait in the safe zone north of pad 5. These teams, 5 south and 5 north, wait until the aircraft has entered the pad, confirmed brakes set, and configured for de-icing. The beta trucks do not monitor a VHF frequency; therefore, the truck teams must wait until receiving a clearance from a ZDC on the UHF radio before manoeuvring their respective trucks into position to de-ice the aircraft. The forward truck on the south side moves to a position forward of the left wing and applies fluid to the top of the aircraft, if required, and from the left wing root outward to the left wing tip. The rear truck on the south side moves into position aft of the left wing and applies fluid to the top of the aircraft, if required, and to the left tail section of the aircraft. Similarly, 5 north de-ices/anti-ices the right side of the aircraft. The forward truck operator on the south side, for an east-to-west traffic flow, is considered the lead of the four-truck formation. This operator is responsible to advise when de-icing starts and holdover time starts. The last operator (the last of the four) to have his/her nozzle closed will advise when de-icing is complete. In addition to the above, the forward truck on the south side is responsible for advising the ZDC that the two trucks on the south are back inside their safe zone. The aft truck on the north side is responsible for advising the ZDC that the two trucks on the north are back inside the safe zone. The south forward truck advises the ZDC with the call 5southsafe when that two-truck team is back in the safe zone, and the north aft truck calls 5northsafe when that two-truck team is back in the safe zone. Should the flow be in a west-to-east direction, the forward north truck is the lead of the four-truck formation and is responsible to advise that the north side is safe. The aft south truck is responsible to advise the ZDC that the south side is safe. The ZDC after the de-icing/anti-icing process is complete then passes a de-icing strip to Iceman. Iceman cannot see all the pads or trucks operating at the CDF. Iceman's only method of ensuring that all the de-icing vehicles are clear of the aircraft before issuing taxi instructions is the passing of the de-icing strip from the ZDC to Iceman. Once Iceman receives this strip, it is assumed that de-icing/anti-icing procedures are complete, the aircraft is free of contamination, and all equipment is clear. Iceman then changes the lit signboard from Stop to Exit Now and verbally authorizes the aircraft to taxi to one of the CDF's four exit points. On the evening of the occurrence, only one ZDC was on duty. The operations manager had anticipated a slow evening and had sent the other ZDC home and shut down the second UHF radio. Consequently, one controller was coordinating the operations of four de-icing pads instead of the usual three pads. The de-icing of DLH471 proceeded normally until the operator of beta truck13 noticed that the aircraft's right wing root remained contaminated. Before leaving the area ahead of the right wing and outboard of engine No4, the operator of beta truck 13 attempted to call the ZDC to request permission to approach the aircraft to remove the contaminant. However, he was unable to communicate with the ZDC on the congested UHF. The ZDC heard the call from the operator but was not able to determine which operator was calling and what was being requested. Each time communication was attempted, the transmission was interrupted by another beta truck attempting radio contact. Beta truck operators are not required to hold a restricted radio telephone operator's licence. The CDF has no procedure for a beta truck operator to return to an aircraft to re-apply anti-icing/de-icing fluid. While this was occurring on 5north, 5south had completed de-icing operations on the left side of the aircraft and made the call 5south safe to the ZDC. This transmission was immediately followed by numerous calls from pad5 and pad4 and by an undetermined number of truck operators keying the push-to-talk feature on their radios. The ZDC assumed that 5north and 5south had called safe and passed the de-icing strip to Iceman. Iceman called DLH471 on VHF and advised the pilots that de-icing was complete, of the type of fluid used and the holdover time, and that the aircraft was free of contamination and clear of all equipment. Iceman requested DLH471 to advise when the aircraft would be ready to taxi. DLH471 immediately called ready to taxi. Iceman instructed DLH471 to wait until the signboard changed to Exit Now, then to taxi straight ahead to the Tango exit and hold short of taxiway Mike. Iceman was not aware that beta truck 13 was still in position ahead of the Boeing 747's right wing and changed the signboard to indicate Exit Now. The captain of DLH471 observed the signboard change and, after both flight crew members maintained that they had visually checked through the flight deck windows, increased engine thrust to manoeuvre the aircraft as cleared. Window posts in the flight deck may create a blind spot along the wing leading edges for flight crew seated in either of the two pilot seats and looking outboard at the respective wing tips. The first officer maintains that he looked out the right side window and did not recall seeing anything ahead of the right wing. The CDF is a completely marshalled environment; the flight crew has no regulatory obligation to check for obstructions before moving the aircraft. The leading edge of the right wing, outboard of engine No4, struck the extended boom of beta truck13 four feet below the operator's cab, and the truck tipped over on its right side. The driver/operator of a beta truck working on pad4 saw truck13 tip over and radioed a Mayday to the ZDC over the UHF. The ZDC informed Iceman, who instructed all aircraft at the CDF to hold their positions and DLH471 to shut down all engines. The ZDC and Iceman then began advising and coordinating airport emergency services. The occurrence took place several hours after official sunset; however, the CDF is well lit. Weather conditions were not a factor, and ground visibility was not obscured.